The present invention relates generally to synchronizers for manually-shifted power transfer devices and, more particularly, to an improved strut-type synchronizer.
Strut-type synchronizers, as used in manually-operated transmissions and four-wheel drive transfer cases, generally include a plurality of spring-biased struts that are radially interposed between a clutch hub fixed for driven rotation with a mainshaft and a sliding clutch sleeve. A spring member is typically installed between the clutch hub and the strut for radially biasing the strut into a central detent groove formed in the clutch sleeve. As is known, the clutch sleeve is splined to the clutch hub for common rotation therewith. Moreover, axial displacement of the clutch sleeve causes the struts to initially move with the clutch sleeve until the struts engage a blocker ring that is also coupled for driven rotation with the clutch hub and which blocks further axial displacement of the clutch sleeve until speed synchronization is complete. Specifically, such axial movement of the struts causes energization of the synchronizer which, in turn, causes frictional engagement between facing surfaces on the blocker ring and a non-driven speed or ratio gear for generating sufficient torque therebetween to "clock" the blocker ring to an indexed position and rotatably drive the ratio gear. Synchronization is achieved when the relative speed between the blocker ring and ratio gear approaches zero. Thereafter, continued axial movement of the clutch sleeve is permitted and the spring members are radially compressed for allowing the clutch sleeve to pass over the struts. In this manner, internal clutch teeth formed on the clutch sleeve are permitted to pass into meshed engagement with external clutch teeth formed on the ratio gear for transmitting power (i.e., drive torque) from the mainshaft to the ratio gear.
Strut-type synchronizers, such as the type disclosed in commonly-owned U.S. Pat. No. 5,113,986 to Frost, additionally have the ability to completely "de-energize" upon disengagement of the clutch sleeve from the ratio gear when the synchronizer is returned to a "neutral" position. In particular, as the synchronizer is selectively de-energized, the spring member imparts an axially directed force on the blocker ring for urging the blocker ring to retract toward a "non-energized" position. Even when the blocker ring is in the non-energized position, the spring member continues to apply an axial biasing force thereon for inhibiting self-energization due to residual viscous effects acting on the synchronizer. In addition, commonly-owned U.S. Pat. No. 5,085,303 to Frost discloses a strut-type synchronizer including a clutch shift sleeve having a profiled internally splined surface that is adapted to coact with the struts for counteracting normal drag forces produced due to axial movement of the clutch sleeve. The spline tooth "profile" was developed to minimize frictional resistance to axial movement of the clutch sleeve, thereby promoting improved "shift feel".
While strut-type synchronizers function satisfactorily for their intended purpose, a problem associated with many strut-type synchronizer is the difficulty associated with assembling the plurality of components into the synchronizer assembly. Additionally, once the spring and strut have been installed between the clutch hub and sliding clutch sleeve, the spring has the tendency to twist and/or become dislodged.